Furnace pouring and casting system

ABSTRACT

The disclosure covers a furnace system including therein a furnace or ladle having a good-sized reservoir which is fludically coupled to a tower, called a charging tower, into which molten material from the reservoir is to be drawn by suction. The molten material is then transmitted under pressure into the cavity of a mold system, and the path from the charging tower to the mold system may include a second tower, called a pouring tower. Although both towers are fluidically connected to the reservoir the connections are arranged to prevent or reduce to an acceptable minimum, the back-flow of the molten material to the reservoir.

United States Patent Groteke et al. 1 Apr. 4, 1972 54 FURNACE POURING AND CASTING 3,268,960 8/1966 Morton ..l64/257 SYSTEM 3,310,850 3/1967 Armbruster 164/64 lnventors: Daniel Edward Groteke; Donald Keith Lazor, both of Louisville, Ky.

Assignee: American Standard Inc., New York, NY.

Filed: June 12, 1969 Appl. No.: 832,792

References Cited UNITED STATES PATENTS Morgenstern... Rearwin Adams..... Morton ..164/257 FOREIGN PATENTS OR APPLICATIONS 1,384,277 ll/1964 France 1 64/337 Primary ExaminerJ. Spencer Overholser Assistant ExaminerJohn E. Roethel Attorney-Jefferson Ehrlich, Tennes I. Erstad and Robert G. Crooks [5 7] ABSTRACT The disclosure covers a furnace system including therein a furnace or ladle having a good-sized reservoir which is fludically coupled to a tower, called a charging tower, into which molten material from the reservoir is to be drawn by suction. The molten material is then transmitted under pressure into the cavity of a mold system, and the path from the charging tower to the mold system may include a second tower, called a pouring tower. Although both towers are fluidically connected to the reservoir the connections are arranged to prevent or reduce to an acceptable minimum, the back-flow of the molten material to the reservoir.

37 Claims, 14 Drawing Figures Patented A ril 4, 1-972 $653,426

7 Sheets-Sheet 1 NZ FA FIGURE I INVENTORS DONALD K. LAZOR DANIEL E. GROTEKE A TORNEY Patented A ril 4, 1972' 3,653,426

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7 sheets sheet 4 FIGURE? FIGURES APREFERENTIAL FLOW RESTRICTIVE FLOW 3H CKS O R HCK V FIGURE9 FIGURE IO INVENTORS DONALD K. LAZOR DANIEL E. GROTEKE g fl K J ATTORNEY Patented April 4, 1972 3,653,426

7 Sheets-Sheet 5 CTC CHT

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7 Sheets-Sheet 6 VTC VACUUM 152}: v VTP WC 7 WP VACUUM VENT 1 VENT 7 PVC D D Q PTP PRESSURE Q o O OQOOUOOOOHOOJOODODOQ I HCN CNC FIGURE E3 mv'snrons DONALD K. LAZOR DANIEL E. GROTEKE ATTORNEY Patented April 4, 1972 3,653,426

7 Sheets-Sheet '7 FIGURE l4 INVENTORS DONALD K. LAZOR DANIEL E. GROTEKE Mp 1 I ATTORNEY FURNACE POURING AND CASTING SYSTEM This invention relates to furnace systems for casting or molding operations. More particularly, this invention relates to furnace systems which may be coupled to molding apparatus so that liquid metal may be repeatedly and regularly fed to the molding apparatus for the purpose of producing castings in more or less regular sequences.

It is not uncommon in the art to interconnect a furnace or ladle to a molding apparatus and to produce a casting by applying pressure to the furnace or ladle so as to force the metal into the molding apparatus. Such furnaces, however, are limitedin the amount of fill pressure that may be applied, and this influences the resultant fill rates of the mold cavities connected thereto. Such types of equipment, if designed to sustain applied pressures equal to those higher pressures that may be developed with the furnace of the present invention, require much more massive construction and are therefore more costly to provide an equivalent function. Also, existing furnaces do not lend themselves to a fully continuous operation because interruptions in the production of castings are brought about by the periodic requirement to open a charging chamber either to add metal to the furnace, or to replace a spent ladle with a fresh ladle full of metal. Such types of equipment require, therefore, an additional amount of labor to operate and generate lost time in the production of castings.

One of the principal objectives of the present invention is the provision of a furnace and molding apparatus so oriented and arranged that molten metal may be fed from time to time, either regularly or intermittently to the molding apparatus, so that castings may be produced at a rather rapid rate and at a relatively low cost.

It is a further objective of this invention to so orient and arrange a furnace to a molding apparatus that castings may be produced rather rapidly, either regularly or intermittently, and the quality of the casting produced in each operation will be relatively high quality and, at the same time, will be low in cost and will require a minimum amount of labor.

It is a further objective of this invention to provide arrangements capable of filling the cavity of a molding apparatus either rapidly or slowly, as may be desired, depending on the requirements determined either by the cast product configuration, or by the molding apparatus construction, or by a combination of these factors.

It is a further objective of this invention to provide arrangements for producing a liquid metal pressure in the molding apparatus cavity substantially higher than the pressures conventionally produced either by normal gravity casting methods or by common pressure-pour casting apparatus, whereby an improvement in the quantities of the final cast product, such as the density, would be provided.

It is a further objective of this invention to provide arrangements fully adapted to casting most metals.

It is a further objective of this invention to provide arrangements whereby the supply of metal to be cast may be replenished fairly rapidly, without significant or major interruption to the production schedule.

I It is a further objective of this invention to provide a production arrangement whereby the system is made up, in part, of a basically standard, non-pressurized commercial furnace with no significant restriction as to its size or capacity, and made up, in its remaining parts, of a pressurized casting structure whose configuration is determined primarily by the desired service conditions for casting the product or a series of products.

In other words, in accordance with this invention, in its relatively simple and basic arrangements, a furnace or ladle is connected to two towers which may be vertically arranged with an interconnection between the two vertical towers and another interconnection to the furnace. One of the towers, which may be called the pouring tower, will be mechanically connected or coupled to a mold system so that liquid metal fed through the pouring tower may fill the spaces of the mold system to create a casting. The second tower, which may be called a charging tower, is provided to receive molten metal from the furnace and thereafter re-feed the molten metal to the pouring tower to supply molten metal to the mold system under pressure to yield a casting.

The two towers are essentially interconnected with the furnace and suction is applied to the charging tower to cause molten metal in the furnace to be drawn into, and therefore supplied to, the charging tower. Thereafter, the suction is removed from the charging tower and pressure is then applied to the charging tower so as to cause the molten metal in the charging tower to be fed through the pouring tower and into the cavity of the mold apparatus so that sufficient material under appropriate pressure will fill the cavity and the cavity will remain filled under such pressure until the casting has been formed. The casting in the mold system is then removed, or the entire mold system is then removed and replaced, so that a new casting may be formed.

The pouring tower may be subjected to suction, during the above described cycle of operation, to facilitate or enhance the casting operation. This suction may be applied in various manners to meet the required characteristics of the molding problem. For example, suction may be supplied to the pouring tower and mold system at the same time that suction is applied to the charging tower, thereby drawing molten metal into both towers. The same intensity of suction need not be applied to both towers if it is desired to achieve difierent molten metal levels in the two towers, or to overcome different hydraulic resistances to flow inherent in the filling of the towers. Altemately, it may be desired to apply suction to the pouring tower at some time after suction is applied to the charging tower. Conversely, the application of suction to the pouring tower may be omitted entirely if it is of no significant benefit to a particular molding operation, or if the mold system to be used is not readily adaptable to suction pressures.

In addition, the same intensities of suction need not be applied to the charging tower and pouring tower on successive cycles of casting, due, for example, to varying levels of molten metal in the furnace reservoir. Indeed, the preferred method of operation would be to arrange to vary the intensities of suction somewhat from cycle to cycle, to overcome the effect that a change in the furnace reservoir level would have in the filled level of the towers, to maintain the tower metal levels at their optimum. Also note that the pressure applied to the charging tower, and the intensities of suction applied to the charging tower, and to the pouring tower, need not be constant throughout a casting cycle, but may each vary in some regular manner to suit the needs or convenience of the particular casting operation, which may perform best under predetermined changing pressure levels.

One arrangement of this invention employs between the furnace and the mechanism which interconnects the two towers a so-called choke spool. The choke spool is provided to prevent an undue amount of molten metal from by-passing the pouring tower and returning to the furnace. In other words, molten metal is to be transported from the furnace to the charging tower so that the charging tower may be filled to a predetermined amount and thereafter subjected to pressure to transport the molten metal through the pouring tower into the cavity of the mold apparatus, substantially without allowing an excessive amount of the molten metal to be returned to the furnace. This is one of the main features of the arrangement described in this invention.

As an alternative to the so-called choke spool, a mechanically actuated stopper device may be interposed to obstruct the channel between the furnace and the two towers, and its mechanism arranged so that in the appropriate phase of the cyclical operation of the charging tower, the stopper device will be operated to present a more or less effective blockage to impede in a very large degree the flow of the molten metal from the charging tower to the furnace.

This invention, together with its objects and features, may be better understood from the more detailed description and explanation hereinafter following when read in connection with the accompanying drawing in which FIG. 1 illustrates a schematic of a lateral elevational view, partly in section, of one form of apparatus for carrying out this invention; FIG. 2 illustrates an end elevational view, partly in section, of the apparatus shown in FIG. 1; FIG. 3 shows a plan view of the ap paratus of FIG. 1; FIGS. 4, 5, and 6 show schematically different arrangements for interconnecting the principal components of the embodiment shown in FIG. 1; FIGS. 7 and 8 show an elevational axial cross sectional view and an end view, respectively, or another form of one of the components, i.e., the choke spool, which may be used in the practice of this invention; FIGS. 9, 10, and 11 illustrate, respectively, a plan cross-sectional view through the orifice centerline, an elevational view, and an end view of another form of the same component, i.e., the choke spool, which may be used in the practice of this invention; FIG. 12 illustrates a lateral elevational view, partly in section, of a modified embodiment of the arrangements shown in FIGS. 1, 2, and 3 in which the choke spool is replaced by a mechanical blockage system; FIG. 13 illustrates an end view, partly in section, of the embodiment shown in FIG. 12; and FIG. 14 represents a plan view of the FIG. 12 equipment.

Throughout the drawing the same or similar parts will be designated by the same reference characters.

Referring more specifically to FIGS. 1, 2 and 3, the reference character F designates a furnace or ladle for molten metals such as iron, steel, brass, zinc or other metals, CT designates the charging tower, and PT designates the pouring tower. The furnace F is connected to the pouring tower PT and to the charging Tower CT by means of a choke spool CKS and a connector spool CNS as shown.

The furnace F may include a filling spout FS through which molten metal may be fed from any source, either continuously or intermittently, as may be desired, a liquid reservoir LR into which the molten metal is fed through the spout FS, a cover CV and a so-called heel weir HW, and an aperture FA which is located in the wall of the furnace F. The furnace F and it cover CV are made up essentially of a shell Sl-I preferably made of steel, adjacent to which there is a refractory lining material RL. The end of the furnace F is provided with a nozzle NZ through which the aperture FA is positioned. The furnace may be equipped with any suitable means for heating the molten metal in reservoir LR.

Molten metal reaching the reservoir LR of furnace F may attain a level, such as L, in the reservoir LR. Whenever the liquid level in the reservoir LR is higher than the peak of the weir HW, liquid will flow into the opening HWO of the weir HW so as to reach the aperture FA. On the other hand, whenever the molten metal in the reservoir is brought below the peak of the weir l-IW, there will be no flow of liquid through the opening HWO and into the aperture FA. This is a structural and operational feature of our equipment. It enables a minimum amount of molten metal to be retained within the reservoir LR under certain conditions in which, for example, it may be desired to make repairs or changes in other components of the overall system. Flooding or leakage of the molten metal is therefore obviated.

The charge tower CT consists of a similar shell SH which may also be made of steel, adjacent to which there is a refractory lining material such as RL. The charging tower CT may include an electrical heating coil I-lCC which may be supplied with electric current to maintain a substantially uniform temperature within the charging tower CT. The charging tower CT also embodies a cap CTC for closing the upper end of the charging tower. The charging tower also includes a channel CHT into which the molten metal fed from the furnace F through the choke spool CKS and the connector spool CNC may be received. The molten metal in channel CHT may thereafter be forced, under pressure, into the pouring tower PT as will be explained. The channel CHT of the charging tower CT is connected to appropriate equipment for inducing a vacuum or negative pressure into the channel CHT, or for supplying a positive pressure into the channel CHT, or for releasing the prevailing pressure to an atmospheric vent. The

FIG. 2 arrangement illustrates piping interconnecting charging tower CT with three separate valves VTC, PVC, and VVC which are connected respectively to a vacuum or negative pressure source, a positive source of gaseous pressure, and an atmospheric vent, the connection being established via the pipe CTP of the charging tower CT.

The pouring tower P'T likewise includes a shell such as SH and a lining RL. The pouring tower PT preferably also includes an electrical heating coil HCP which may be employed to maintain a predetermined temperature in the pouring tower PT. The pouring tower PT also includes a channel CHP which is axially positioned within the pouring tower and is in line with the opening to the mold system MS which may be seated or otherwise mounted on the pouring tower PT. The mold system MS embraces a suitable cavity MSC which is to be filled under appropriate pressure by the molten metal driven through the channel CHP. The cavity MSC is connected by suitable piping to similar valve devices VTP and VVP for respectively applying a negative pressure, if desired, through the cavity of the mold system MS to the channel CHP, or to vent the channel CHP, the connection being established via pipe PTP of the pouring tower PT. Note that although the drawing shows valve devices VTP and VVP as remote devices connected to mold system MS, equivalent devices may be installed as integral parts either of mold system MS, or pouring tower P1", or an adapter mounted between the mold system and the pouring tower. These equivalent devices may be either mechanically actuated components, or non-moving portions of the structure which depend on the configuration or choice of material to provide an inherent valving action, or a combination thereof. Further note that in those applications of this invention wherein suction is not applied to pouring tower PT, and in which the mold system MS is constructed of porous material or whose cavity is otherwise vented to atmosphere, valve devices VTP and VVP would not be required, and would not apply to the system.

The charging tower CT and pouring tower PT are connected to each other by the connector spool CNS, which, as is seen more clearly from FIG. 2, provides a channel CNC interconnecting the channel CI-IT of the charging tower CT to the channel CHP of the pouring tower PT. The channel CNC of the connector spool CNS also interconnects channels CHT and CI-IP with the aperture of choke spool CKS, as seen more clearly in FIG. 3.

The connector spool is preferably also provided with an electrical heating coil I-ICN for the purpose of assisting in maintaining the fluid transport through the connector spool at a desired temperature. It is especially important to maintain a suitable temperature in the connector spool CNS to inhibit the freezing or solidifying of metal in its channel CNC.

In a normal operation of the equipment of FIGS. 1, 2 and 3, the initial level of the molten liquid in the charging tower CT and in the pouring tower PT will be essentially the same as the level L in the furnace F. The vacuum valve or valves VTC and VTP connected respectively to the charging tower CT and to the pouring tower PT will then be open simultaneously to apply a sufficient negative pressure to, that is, to draw the molten metal into, the channels CHT of the charging tower and CI-IP of the pouring tower PT to a common liquid level such as L1. This will be accompanied by a corresponding lowering of the level in the furnace F to about L2. The pressure valve PVC connected to the charging tower CT will then be opened so as to supply a gaseous mixture to the channel CI-IT to drive the level of the liquid in channel CHT downwardly under the influence of the applied pressure. This will lower the level to a point such as, for example, L3, This will cause the fluid in the channel CHP of the pouring tower PT to move upwardly into the cavity MSC of the mold system MS to fill the cavity to a predetermined pressure. After a predetermined time interval, the liquid at the point of entry to the cavity MSC will be solidified so that the mold system may then be opened and the casting therein removed. If desired, the mold system MS may be removed by any well known means for subsequent casting ejection. Before opening or removing the mold system MS, the pressure valve PVC, previously connected to the charging tower CT, will be closed and the vent valve or valves VVP and VVC connected to the pouring tower PT and the charging tower CT respectively will be opened to bring the upper regions of the channels CHT and CI-IP to about atmospheric pressure. Upon venting the towers and the mold system to atmospheric pressure, the metal level within the charging tower CT, the pouring tower PT, and furnace F will be returned to substantially the same, or almost the same, initial level such as L. Following removal of the casting within the mold system MS, or the removal and replacement of the mold system MS,

the full cycle may be repeated again and again.

Briefly, the molten metal in the furnace F, which may be, for example, an electrical furnace, constitutes a reservoir which may be kept full but is to be tapped step by step. The first step involves drawing or otherwise supplying the molten metal to a satellite charging tower CT which may be accomplished by suction. Then pressure is applied to the liquid in the satellite charging tower CT to drive the liquid therefrom, via

the so-called pouring tower PT, to the cavity MSC of the mold system MS, not only to fill the cavity but also to maintain a predetermined pressure on the liquid in the cavity for a predetermined time interval. The time interval should be sufficient to allow the liquid to solidify sufficiently to form a frozen metal barrier at the gate MSG of the mold system so that the mold system MS may be removed and replaced by another like mold system, while the original casting undergoes its thorough solidification. Or, the mold system MS may be held in position under pressure until the necessary and complete solidification has occurred therein so that the casting may then be ejected by any well known means. The channeling and interconnecting equipment is designed to permit adequate charging flow from the furnace F to the charging tower CT, but inhibit the return flow to the furnace F when the positive pressure is applied to drive the fluid into the cavity MSC of the mold system MS.

In the earlier description of this invention it was indicated that equal suctions were applied simultaneously to both towers CT and PT before pressure was applied to drive the molten metal into the cavity MSC of the mold system MS. If desired and as already suggested, the equipment may be organized and operated wherein unequal suction would be applied simultaneously to both towers CT and PT, or wherein equal or unequal suctions would be applied first to the charging tower CT and then sequentially to the pouring tower PT, or wherein suction would be applied to charging tower CT only with the pouring tower PT and the mold system cavity MSC remaining vented to atmosphere at all times. Further, the pressure applied to charging tower CT, or the intensities of suction applied to the charging tower CT and pouring tower PT, need not remain constant throughout a casting cycle, but may each be varied separately in some regular manner during the casting cycle.

By a judicious selection of pressure and suction parameters together with equipment sizing and mold design parameters, various distinctly different casting effects may be achieved. For example, pouring tower PT may be filled nearly full of molten metal by suction, with the subsequent initial pressure applied to charging tower CT regulated to provide the desired rate of entry of molten metal into mold cavity MSC. This rate of entry may range from relatively slow to relatively fast, and would depend primarily on the configuration of the mold cavity MSC and gate MSG, and the static pressure of the molten metal entering the mold cavity MSC. The same results, a desired rate of entry into mold cavity MSC ranging from relatively slow to relatively fast, could be achieved with the pouring tower PT filled to a significantly lower level by suction or by gravity. In this instance, however, a relatively rapid rate of entry of molten metal into a mold cavity MSC would be aided by the velocityacquired by the molten metal stream as it approachesthe mold system MS. An application of a more intense suction into pouring tower PT than the suction intensity used to fill pouring tower P1, with this more intense suction applied after the molten metal has reached the desired level in pouring tower PT, would reduce the intensity of pressurization required in charging tower CT, thereby also reducing the amount of back flow through a choke spool CS, and would also reduce the amount of gas entrapped in a closed mold cavity MSC and hence entrapped in the final cast product. An application of a more intense pressure into charging tower CT than the pressure used in filling a closed mold cavity MSC, with this more intense pressure applied after mold cavity MSC is filled, would provide higher density in the final cast product. A requirement inherent in this invention, if a solid casting is desired, is that pressure be maintained in charging tower CT until liquid metal flow out of mold cavity MSC is prevented by, for example, a frozen metal barrier at mold cavity gate MSG. However, with a suitable mold MS design, pressure may be maintained in charging tower CT for a sufficient length of time so that the molten metal in pouring tower channel CHP would act as a riser for the casting until a frozen metal barrier formed at mold cavity gate MSG at a delayed time, thereby tending to overcome solidification shrinkage in the final cast product.

The mold system MS may be an integral part of an automatic indexing system so that a mold system, or series thereof, may be filled and withdrawn at specified intervals which are repeated and repeated.

FIG. 4 shows a re-arrangement of the pouring tower PT, the charging tower CT, and the choke spool CKS, arranged in a somewhat different physical relationship to furnace F. FIG. 5 shows still another re-arrangement of the several components. Likewise, FIG. 6 illustrates a further layout of these components. Although it is shown in FIGS. 4, 5 and 6 that the charging tower CT is conveniently interposed between the pouring tower PT and the furnace F, other arrangements may be used if they provide suitable hydraulic paths. The pouring tower and the charging tower, although shown as somewhat adjacent to the furnace, may be considerably removed from the furnace, perhaps even in a different structure or building. Thus, the choke spool CKS may be a rather lengthy coupler extending over a long distance. The greater the distance, however, the greater will be the amount of heat that must be supplied by the heating coils incorporated in the choke spool CKS or in the other components to maintain the temperature of the liquid therein at the predetermined or desired valves. Alternately, various specific organizations of equipment and casting requirements may be such that a separate and distinct choke spool would not be required. In such cases, the functional requirement provided by a choke spool would be, instead, provided by the remaining channels interconnecting the furnace reservoir LR with the charging tower CT and the pouring tower PT. Therefore, in such cases, a separate and distinct choke spool may be omitted from the system without departing from the spirit and intent of this invention.

FIGS. 7 and 8 show a modified form of choke spool CKS which is supplied with a heating coil HCl( and is of similar construction to the choke spool CKS of FIGS. 1 to 3. However, the channel, which is shown more clearly in FIG. 7, is shaped so that molten metal may move more freely in the furnace-to-towers direction, or right-to-left as shown in FIG. 7, than in the reverse direction. The channel is designed to provide a larger hydraulic restriction in one direction of flow by a purposeful inclusion of discontinuities and swirling or eddy action in that direction of flow only, and to provide a minimum hydraulic restriction in the other direction of flow by avoiding discontinuities and swirling action in that direction of flow. The properties and requirements of such a design will be readily understood by those skilled in the field of fluid dynam- ICS.

FIGS. 9, 10 and 11 illustrate still another pattern for the channel of the choke spool CKS. This flow path also depends upon eddy paths to accomplish preferential flow in one direction.

The channel of FIGS. 7 and 8 and the channel of FIGS. 9, 10 and 11 are considerably different from the substantially uniform channel of choke spool CKS of FIGS. 1, 2 and 3. In the latter arrangement, the channel is of straight cylindrical shape and operates with a considerable reduction in diameter when compared with the diameter of the aperture FA of the furnace F or the channel of the connector spool CKS, or when compared to the minimum diameter of an equivalently shaped channel as shown in FIG. 7 and FIG. 9.

FIGS. 12, 13 and 14 differ essentially from the arrangements of FIGS. 1, 2 and 3 in that no choke spool CKS is employed. In FIGS. 12, 13 and 14, however, a stopper valve as sembly SVA is employed with includes a poppet valve SVP for closing the aperture FB leading from the furnace F to the channel CHT of the charging tower CT. The poppet valve SVP may be controlled in any well known manner, as, for example, by a hydraulic cylinder arrangement I-IC which, when actuated, drives the poppet valve SVP downward to close the aperture PE in the furnace F and, when actuated in the reverse direction, causes the poppet valve SVP to be moved upwardly to reopen the aperture FB. The bottom of valve SVP and the head of the aperture FB of furnace F may be brought into bodily contact with each other when the piston SVP is moved into its lower position, but a tight and perfect closure need not be formed to sufficiently restrict the channel leading from the towers to furnace F. By closing or substantially reducing the gap between the poppet valve SVP and the aperture FB of the furnace F, it is possible to prevent or minimize back flow of molten metal through the connector spool CNS to the furnace F. The substantial closure of the aperture FB of the furnace F should be completed just prior to the opening of the pressure valve PVC for feeding the fluid to the mold system, so that the change in pressurization then occurring will not drive the fluid backward into the furnace F.

Note that the major components of this form of the invention may also be conveniently rearranged, so that arrangements similar in nature to those shown in FIG. 4 and FIG. 5, for example, may also be obtained. Also, although a choke spool is specifically omitted from this form of the invention, a supplemental connector spool may be employed to further enhance the arrangement of components obtainable with this form of the invention. This supplemental connector spool could be similar, in construction and placement, to the choke spool CKS shown in FIG. 1, except that the internal channel would be of substantially the same diameter as that used in connector spool channel CNC or furnace aperture FA.

The furnace used in this invention may be one which is basically a standard furnace or ladle, constructed for non-pressurized operation, but which is so arranged and coordinated with respect to the two coupled towers CT and PT that it is used in a system which is, in general, full pressurized. The use of positive pressure is essential for producing a casting with the mold system MS. The furnace, because of its large reservoir of molten metal for repeated and rapid casting operations, is not readily convertible to the necessary pressurization.

However, pressurization is accomplished, in accordance with this invention, with a furnace which is itself not pressurized and is not itself suitable for the pressure requirements.

The general arrangement of this invention, in employing a combination of a charging tower CT and a pouring tower PT remote from the main furnace body, conveniently permits the economical development of higher pressures for filling and compacting the metal in the mold cavity. Consequently, the casting has substantially higher density and contains very few, if any, voids.

The arrangement of this invention is usable with, but is not limited to, forms of mold systems capable of sustaining a vacuum within their major cavities. Indeed, the mold system may even be a substantially permanent arrangement, such as a die casting machine, for continuous or repeated operations over long intervals of time. The pouring tower PT is basically a sturdy configuration and is amenable to the ready mounting of any mold or to connecting to any machine indexing system. Since the pressurizing gas medium is not in direct or proximate contact with the metal entering the mold cavity MSC, problems of gas aspiration through refractory members, common to many other pressure pour systems, are avoided, thereby eliminating this cause of porosity in the cast product.

It will be observed that heating coils are provided both in the towers and in the components interconnecting the towers with each other and with the furnace. These heating coils avoid solidification of the metal in the transfer channels, and they maintain the metal to be cast in the mold cavity MSC at its optimum temperature. It will be noted that with the systems depicted, the optimum temperature can be maintained even when the mold system is positioned at a point which is considerably remote from the furnace.

It will be noted that the metal used in casting is taken from within the furnace F well beneath the normal slag level and is thus reasonably clean and free of non-metallic inclusions. The arrangement is such, moreover, that the mechanism of this invention lends itself either to fast fill rates or slow fill rates, as may be desired, for different types of cast product or mold structures. A relatively slow fill rate will reduce turbulence associated with filling of the mold cavity and thus will permit, through the elimination of porosity caused by the turbulent entrapment of mold gasses, the development of higher cast densities in the final product. Also, a relatively slow fill rate will permit use of molds containing intricate or fragile core structures that would otherwise be damaged by a high velocity entry of metal. Conversely, a faster fill rate will permit the forming of cast products with relatively thinner walls. Also, in a system in which a vacuum is drawn in the mold cavity MSC and in the pouring tower PT, porosity caused by entrapment of mold gasses will be reduced, thus permitting the development of higher cast densities in the final product. Thus, the cast product will be of a higher quality.

The use of a remote charging tower CT containing a reduced quantity of metal obtained from the main furnace bath or reservoir permits a further advantage when pouring metals requiring delayed treatment prior to pouring to develop optimum metallurgical properties. Typical of such materials are nodular irons, gray irons, or hypereutectic aluminum silicon alloys. The benefits developed from such treatments are normally time dependent and thus the treatments lose their effects if the metal is held for extended periods of time. Thus, through the use of direct treatment in the charging tower CT, near optimum utilization of the inoculant may be developed by virtue of treatment just prior to pressure filling of the mold system with the treated metal. Treatment of metal in the main furnace bath would be less efficient by virtue of a requirement for more frequent treatment to maintain the same level of benefit because of the fading characteristics of the treatment.

The furnace F is depicted as a reservoir of molten material, i.e., molten metal, which is itself maintained at about atmospheric pressures. It may be any basically standard vented melting or holding furnace which is adapted for incorporation in the furnace system of this invention. The furnace may employ any suitable means for heating the molten metal in reservoir LR. However, as already stated, the furnace F or its reservoir is an important component of the overall furnace system which, according to the present invention, is operated at higher pressures and higher filling and flowing velocities. The furnace system, therefore, lends itself to automation for the rapid production of quality castings, even intricate structural formations, as already noted. Although described in reference to its use with molten metals, the invention is readily usable, or adaptable for use, with other materials, such as molten plastics, ceramic slips, or other viscous or non-viscous or other materials whether metallic or not.

The furnace system of this invention can handle any form of mold system or structure, ranging from sand molds to permanent molds, which are inherently adaptable, or which may be adapted, to the desired casting cycle. Temperatures can be maintained in the various components at optimum values due to the local electrical heaters employed. As previously noted, the poured metal, which is taken from within the inner segments of the reservoir, is substantially free of slag. The suction or vacuum operation in drawing molten material from the reservoir reduces or eliminates the presence of entrapped gases. Moreover, the suction used for filling the pouring tower may be maintained for any required time interval so as to degasify the poured metal. Pressurization of the molten material, which is to be driven into the cavity of the mold system, may economically be performed with inert gases, especially because a relatively small volume of gas is required for pressurizing the tower structures.

While this invention has been shown and described in certain particular arrangements merely for illustration and explanation, it will be apparent that this invention may be embodied in many and widely different arrangements without departing from the spirit and the scope of this invention.

What is claimed is:

1. Liquid dispensing apparatus comprising a non-pressurized liquid reservoir, a pouring tower, a charging tower, a mold system fluidically coupled to said reservoir through the pouring tower and the charging tower, means for applying negative pressure to the charging tower to draw liquid from the reservoir into the charging tower, means for applying positive pressure to the liquid in the charging tower in order to drive liquid through the pouring tower and into the mold system, and means for substantially preventing the backflow of liquid into the reservoir in response to the application of pressure to the liquid in the charging tower.

2. A liquid dispensing apparatus according to claim 1 in which the backflow preventing means includes a choke spool interposed in the coupling between the reservoir and the pouring and charging towers to substantially prevent the return flow of liquid to said reservoir.

3. Liquid dispensing apparatus according to claim 1 in which a movable stopper is interposable in the discharge path of the reservoir physically to obstruct the flow of liquid back to the reservoir when pressure is applied to the liquid in the charging tower.

4. Liquid dispensing apparatus according to claim 1 in which the reservoir includes a weir to bar the flow of liquid from the reservoir when the level of the liquid recedes below the barrier of the weir.

5. Liquid dispensing apparatus comprising a non-pressurized reservoir containing liquid, a charging tower, a pouring tower, said towers being fluidically coupled continuously to each other and to said reservoir, means for applying suction to said charging tower to draw liquid from said reservoir into said charging tower, a mold system positioned above the pouring tower so that liquid discharged under pressure from the charging tower may be supplied to said mold system, and means for applying pressure to the liquid in said charging tower to deliver liquid from said charging tower through said pouring tower to said mold system without returning an excessive amount of said liquid to said reservoir.

6. Liquid dispensing apparatus comprising a non-pressurized reservoir containing liquid, a charging tower, a pouring tower, said towers being fluidically coupled continuously to each other and to said reservoir, means for applying suction to said charging tower to draw liquid from said reservoir into said charging tower, a mold system positioned above the pouring tower, means for applying pressure to the liquid in said charging tower to deliver liquid from said charging tower through said pouring tower to said mold system, and a choke spool interposed between the reservoir and the coupling extending from said reservoir to said charging tower and said pouring tower for substantially preventing the backflow of liquid to said reservoir when pressure is applied to the liquid to deliver said liquid through the pouring tower to the mold system.

7. Liquid dispensing apparatus comprising a non-pressurized reservoir containing liquid, a charging tower, a pouring tower, said towers being fluidically coupled continuously to each other and to said reservoir, means for applying suction to said charging tower to draw liquid from said reservoir into said charging tower, a mold system seated on top of the pouring tower, means for applying pressure to the liquid in said charging tower to deliver liquid from said charging tower through said pouring tower to said mold system, and a preferential choke spool inserted into the coupling between said reservoir and the connection established between both towers for substantially preventing the backflow of liquid to said reservoir when said mold system is being filled by the liquid discharged through the pouring tower.

8. Liquid dispensing apparatus comprising a non-pressurized reservoir containing liquid, a charging tower, a pouring tower, said towers being fluidically coupled continuously to each other and to said reservoir, means for applying suction to said charging tower to draw liquid from said reservoir into said charging tower, a mold system seated on top of the pouring tower to receive liquid discharged through the pouring tower under pressure, means for applying pressure to the liquid in said charging tower to deliver liquid from said charging tower through said pouring tower to said mold system, and a mechanical stopper inserted in the path of the coupling between said reservoir and said towers to prevent the backflow of any substantial amount of said liquid to said reservoir when it is being transmitted under pressure through the pouring tower to fill the mold system.

9. Liquid dispensing apparatus as claimed in claim 1 including heating means for supplying heat continuously to the coupling between the charging tower, the pouring tower and the reservoir for maintaining predetermined temperatures in said coupling.

10. Liquid dispensing apparatus, comprising a non-pressurized liquid reservoir containing molten metal, a charging tower elevated above and connected to said reservoir, a pouring tower also elevated above and connected to said reservoir, a mold system coupled to the pouring tower for receiving metal from the pouring tower, means for applying negative pressure to the charging tower to cause molten metal to be drawn into the charging tower from said reservoir, means for applying positive pressure to the molten metal in the charging tower to cause the molten metal therein to travel through the pouring tower to the mold system, and means for supplying heat to the connections between the charging tower, the pouring tower and the reservoir to prevent the freezing of the molten metal within said connections.

11. Liquid dispensing apparatus according to claim 10 including also a choke spool interposed in the connections between the reservoir and the charging and pouring towers to substantially prevent the return of molten metal to the reservoir when pressure is applied to the molten metal in the charging tower.

12. Liquid dispensing apparatus according to claim 10, in which the reservoir includes a movable stopper to prevent the return of molten metal to the reservoir when pressure is applied to the charging tower.

13. Liquid dispensing apparatus according to claim 10 including means for maintaining predetermined temperatures within the charging tower and the pouring tower.

14. Liquid dispensing apparatus according to claim 10 in which the reservoir embodies a weir to prevent the flow of molten metal from the reservoir except when the level of the molten metal in the reservoir rises above the peak of the weir.

15. A casting system comprising a reservoir of molten metal, a mold system, a charging tower having a substantially vertical cavity fluidically coupled continuously between said reservoir and said mold system, means for applying suction to said tower at spaced time intervals to draw molten metal from said reservoir into the cavity of said tower, means to apply sustained fluid pressure of sufficient magnitude to the cavity of the tower during periods between the spaced intervals to drive molten metal therein into the mold system to fill the cavity of the mold system under said sustained pressure, and

means to substantially inhibit the backfiow of molten metal from said tower to said reservoir whether or not fluid pressure is applied to the cavity of said tower.

16. A casting system according to claim 15 in which the backfiow inhibiting means is positioned in the coupling between the tower and the reservoir and includes a choke spool.

17. A casting system comprising a reservoir of molten metal, a mold system, a charging tower fluidically coupled continuously between said reservoir and said mold system, a second tower fluidically coupled continuously between said charging tower and the mold system so that molten metal from said charging tower will be transmitted under pressure to the cavity of the mold system through the cavity of the second tower, means for applying suction to said charging tower at spaced time intervals to draw molten metal from said reservoir into the cavity of said charging tower, and means to apply pressure to the cavity of the charging tower during periods between the spaced intervals to drive molten metal therein into the mold system to fill the cavity of the mold system under sustained pressure.

18. A casting system according to claim 17 in which the reservoir is continuously maintained in a non-pressurized condition, and the system includes means for substantially barring an excessive amount of pressurized molten metal from being returned to said reservoir.

19. A casting system according to claim 17 in which the mold system is coupled to the charging tower so that its cavity and that of the tower are fluidically coupled continuously to each other and physically adjacent to each other.

20. A casting system according to claim 17 in which the mold system is seated on the second tower so that its cavity is immediately adjacent and fluidically coupled to the cavity of the second tower.

21. A casting system according to claim 20, in which the cavity of the mold system and the cavity of the second tower are immediately adjacent to each other and are fluidically coupled to each other and have a restricted aperture substantially at the interface so that the molten metal may freeze at said interface substantially before the molten metal freezes within the cavity of the mold system.

22. A casting system according to claim 17 in which the charging tower is continuously heated to maintain the molten metal in a liquid state in the cavity thereof and above a predetermined temperature.

23. A casting system comprising a non-pressurized reservoir containing molten material, a mold system, first and second towers fluidically coupled continuously to each other and to said reservoir, means for applying suction to the cavities within both towers so as to draw molten material from said reservoir into said cavities, and means to apply pressure to the cavity of said first tower to drive molten material from said first tower to the cavity of said mold system through the cavity of said second tower to fill the cavity of the mold system under pressure.

24. A casting system according to claim 23 in which the coupling between the reservoir and said towers includes one or more choke spools to substantially prevent the backfiow of molten material from the cavities of said towers to said reservoir.

25. A casting system according to claim 23 in which the reservoir includes a movable stopper for preventing the flow of molten material into said reservoir.

26. A casting system including a reservoir into which molten material is fed through an input port at one side of the base of the reservoir and having a discharge port adjacent the other side of the base of the reservoir, a weir within said reservoir to prevent the fiow of molten material from the discharge port of said reservoir when the level of the molten material therein recedes below a predetermined height, a continuous unidirectional conduit one end of which is coupled to the discharge port of said reservoir to permit the free flow of molten material out of said discharge port but which has a backflow preventer therein as part of the continuous path of said conduit to substantially prevent the return of an excessive amount of molten material to said reservoir, and a mold system which is coupled to the other end of said continuous conduit to receive molten material flowing from the reservoir through said conduit.

27. A casting system according to claim 26 including means to apply gaseous pressure to the molten material fiowing to the mold system and to maintain said pressure for a predetermined time interval after the mold system has been filled with molten material.

28. Dispensing apparatus for high temperature liquids such as molten metal, comprising a non-pressurized reservoir having a discharge port formed in said reservoir formed at the base thereof, a continuous conduit having a choke spool therein and capable of transmitting said liquid substantially in but one direction, a mold system, means for applying suction to the discharge port of said reservoir through said conduit for drawing said liquid from said reservoir to an intermediate receptacle, and means for applying gaseous pressure to said receptacle to drive the liquid therein to said mold system, said conduit substantially opposing the return flow of an excessive amount of said liquid to said reservoir.

29. Dispensing apparatus for high temperature liquids in accordance with claim 28 including a weir at the base of the reservoir for preventing the flow of such liquid from said reservoir when the level of such liquid in said reservoir is below a predetermined level.

30. Dispensing apparatus for high temperature liquids according to claim 28 including a mechanical element movable into said reservoir for substantially closing the discharge port thereof when positive pressure is applied to drive the liquid into said mold system.

31. Dispensing apparatus for high temperature liquids according to claim 28 including also a weir positioned at the discharge port of said reservoir for barring the flow of liquid through the discharge port thereof when the level of the liquid is below the crown of said weir, and a mechanical element to block the flow of liquid through the discharge port when pressure is applied to the mold system.

32. Dispensing apparatus for liquids according to claim 28 including heating means for supplying heat to the liquid leaving the discharge port of the reservoir to prevent the liquid from solidifying when traveling to the mold system.

33. A casting system comprising a mold system, a molten metal source, a receptacle fluidically coupled continuously between said mold system and said source and including means for drawing into said receptacle molten metal from said source by suction, means for supplying pressurized gas for feeding molten metal from said receptacle to said mold system, and choke spool means interposed between said receptacle and said source to permit the unidirectional and substantially free flow of molten metal from said source to said receptacle and to substantially obstruct the return fiow of liquid from said receptacle to said source, said latter means including an aperture of predetermined cross-sectional shape and dimensions through which the molten metal flows rapidly.

34. A casting system according to claim 33 in which heat is continuously supplied electrically to said aperture to prevent the molten metal flowing therethrough from solidifying during the time that it remains within said aperture.

35. A casting system comprising a non-pressurized reservoir containing casting material, a charging tower, a pouring tower, a mold system, substantially airtight couplings fluidically interconnecting said reservoir, said towers and said mold system, means for applying suction to both towers to draw casting material from said reservoir into both towers, means for applying pressure to the charging tower to deliver casting material through the pouring tower to the mold system under continuous pressure supplied to the mold system so as to diminish the presence of voids in the casting material therein.

36. A casting system according to claim 35 in which the couplings include means to freely transmit casting material 

1. Liquid dispensing apparatus comprising a non-pressurized liquid reservoir, a pouring tower, a charging tower, a mold system fluidically coupled to said reservoir through the pouring tower and the charging tower, means for applying negative pressure to the charging tower to draw liquid from the reservoir into the charging tower, means for applying positive pressure to the liquid in the charging tower in order to drive liquid through the pouring tower and into the mold system, and means for substantially preventing the backflow of liquid into the reservoir in response to the application of pressure to the liquid in the charging tower.
 2. A liquid dispensing apparatus according to claim 1 in which the backflow preventing means includes a choke spool interposed in the coupling between the reservoir and the pouring and charging towers to substantially prevent the return flow of liquid to said reservoir.
 3. Liquid dispensing apparatus according to claim 1 in which a movable stopper is interposable in the discharge path of the reservoir physically to obstruct the flow of liquid back to the reservoir when pressure is applied to the liquid in the charging tower.
 4. Liquid dispensing apparatus according to claim 1 in which the reservoir includes a weir to bar the flow of liquid from the reservoir when the level of the liquid recedes below the barrier of the weir.
 5. Liquid dispensing apparatus comprising a non-pressurized reservoir containing liquid, a charging tower, a pouring tower, said towers being fluidically coupled continuously to each other and to said reservoir, means for applying suction to said charging tower to draw liquid from said reservoir into said charging tower, a mold system positioned above the pouring tower so that liquid discharged under pressure from the charging tower may be supplied to said mold system, and means for applying pressure to the liquid in said charging tower to deliver liquid from said charging tower through said pouring tower to said mold system without returning an excessive amount of said liquid to said reservoir.
 6. Liquid dispensing apparatus comprising a non-pressurized reservoir containing liquid, a charging tower, a pouring tower, said towers being fluidically coupled continuously to each other and to said reservoir, means for applying suction to said charging tower to draw liquid from said reservoir into said charging tower, a mold system positioned above the pouring tower, means for applying pressure to the liquid in said charging tower to deliver liquid from said charging tower through said pouring tower to said mold system, and a choke spool interposed between the reservoir and the coupling extending from said reservoir to said charging tower and said pouring tower for substantially preventing the backflow of liquid to said reservoir when pressure is applied to the liquid to deliver said liquid through the pouring tower to the mold system.
 7. Liquid dispensing apparatus comprising a non-pressurized reservoir containing liquid, a charging tower, a pouring tower, said towers being fluidically coupled continuously to each other and to said reservoir, means for applying suction to said charging tower to draw liquid from said reservoir into said charging tower, a mold system seated on top of the pouring tower, means for applying pressure to the liquid in said charging tower to deliver liquid from said charging tower through said pouring tower to said mold system, and a preferential choke spool inserted into the coupling between said reservoir and the connection established between both towers for substantially preventing the backflow of liquid to said reservoir when said mold system is being filled by the liquid discharged through the pouring tower.
 8. Liquid dispensing apparatus comprising a non-pressurized reservoir containing liquid, a charging tower, a pouring tower, said towers being fluidically coupled continuously to each other and to said reservoir, means for applying suction to said charging tower to draw liquid from said reservoir into said charging tower, a mold system seated on top of the pouring tower to receive liquid discharged through the pouring tower under pressure, means for applying pressure to the liquid in said charging tower to deliver liquid from said charging tower through said pouring tower to said mold system, and a mechanical stopper inserted in the path of the coupling between said reservoir and said towers to prevent the backflow of any substantial amount of said liquid to said reservoir when it is being transmitted under pressure through the pouring tower to fill the mold system.
 9. Liquid dispensing apparatus as claimed in claim 1 including heating means for supplying heat continuously to the coupling between the charging tower, the pouring tower and the reservoir for maintaining predetermined temperatures in said coupling.
 10. Liquid dispensing apparatus, comprising a non-pressurized liquid reservoir containing molten metal, a charging tower elevated above and connected to said reservoir, a pouring tower also elevated above and connected to said reservoir, a mold system coupled to the pouring tower for receiving metal from the pouring tower, means for applying negative pressure to the charging tower to cause molten metal to be drawn into the charging tower from said reservoir, means for applying positive pressure to the molten metal in the charging tower to cause the molten metal therein to travel through the pouring tower to the mold system, and means for supplying heat to the connections between the charging tower, the pouring tower and the reservoir to prevent the freezing of the molten metal within said connections.
 11. Liquid dispensing apparatus according to claim 10 including also a choke spool interposed in the connections between the reservoir and the charging and pouring towers to substantially prevent the return of molten metal to the reservoir when pressure is applied to the molten metal in the charging tower.
 12. Liquid dispensing apparatus according to claim 10, in which the reservoir includes a movable stopper to prevent the return of molten metal to the reservoir when pressure is applied to the charging tower.
 13. Liquid dispensing apparatus according to claim 10 including means for maintaining predetermined temperatures within the charging tower and the pouring tower.
 14. Liquid dispensing apparatus according to claim 10 in which the reservoir embodies a weir to prevent the flow of molten metal from the reservoir except when the level of the molten metal in the reservoir rises above the peak of the weir.
 15. A casting system comprising a reservoir of molten metal, a mold system, a charging tower having a substantially vertical cavity fluidically coupled continuously between said reservoir and said mold system, means for applying suction to said tower at spaced time intervals to draw molten metal from said reservoir into the cavity of saiD tower, means to apply sustained fluid pressure of sufficient magnitude to the cavity of the tower during periods between the spaced intervals to drive molten metal therein into the mold system to fill the cavity of the mold system under said sustained pressure, and means to substantially inhibit the backflow of molten metal from said tower to said reservoir whether or not fluid pressure is applied to the cavity of said tower.
 16. A casting system according to claim 15 in which the backflow inhibiting means is positioned in the coupling between the tower and the reservoir and includes a choke spool.
 17. A casting system comprising a reservoir of molten metal, a mold system, a charging tower fluidically coupled continuously between said reservoir and said mold system, a second tower fluidically coupled continuously between said charging tower and the mold system so that molten metal from said charging tower will be transmitted under pressure to the cavity of the mold system through the cavity of the second tower, means for applying suction to said charging tower at spaced time intervals to draw molten metal from said reservoir into the cavity of said charging tower, and means to apply pressure to the cavity of the charging tower during periods between the spaced intervals to drive molten metal therein into the mold system to fill the cavity of the mold system under sustained pressure.
 18. A casting system according to claim 17 in which the reservoir is continuously maintained in a non-pressurized condition, and the system includes means for substantially barring an excessive amount of pressurized molten metal from being returned to said reservoir.
 19. A casting system according to claim 17 in which the mold system is coupled to the charging tower so that its cavity and that of the tower are fluidically coupled continuously to each other and physically adjacent to each other.
 20. A casting system according to claim 17 in which the mold system is seated on the second tower so that its cavity is immediately adjacent and fluidically coupled to the cavity of the second tower.
 21. A casting system according to claim 20, in which the cavity of the mold system and the cavity of the second tower are immediately adjacent to each other and are fluidically coupled to each other and have a restricted aperture substantially at the interface so that the molten metal may freeze at said interface substantially before the molten metal freezes within the cavity of the mold system.
 22. A casting system according to claim 17 in which the charging tower is continuously heated to maintain the molten metal in a liquid state in the cavity thereof and above a predetermined temperature.
 23. A casting system comprising a non-pressurized reservoir containing molten material, a mold system, first and second towers fluidically coupled continuously to each other and to said reservoir, means for applying suction to the cavities within both towers so as to draw molten material from said reservoir into said cavities, and means to apply pressure to the cavity of said first tower to drive molten material from said first tower to the cavity of said mold system through the cavity of said second tower to fill the cavity of the mold system under pressure.
 24. A casting system according to claim 23 in which the coupling between the reservoir and said towers includes one or more choke spools to substantially prevent the backflow of molten material from the cavities of said towers to said reservoir.
 25. A casting system according to claim 23 in which the reservoir includes a movable stopper for preventing the flow of molten material into said reservoir.
 26. A casting system including a reservoir into which molten material is fed through an input port at one side of the base of the reservoir and having a discharge port adjacent the other side of the base of the reservoir, a weir within said reservoir to prevent the flow of molten material from the discharge port of said reservoir when tHe level of the molten material therein recedes below a predetermined height, a continuous unidirectional conduit one end of which is coupled to the discharge port of said reservoir to permit the free flow of molten material out of said discharge port but which has a back-flow preventer therein as part of the continuous path of said conduit to substantially prevent the return of an excessive amount of molten material to said reservoir, and a mold system which is coupled to the other end of said continuous conduit to receive molten material flowing from the reservoir through said conduit.
 27. A casting system according to claim 26 including means to apply gaseous pressure to the molten material flowing to the mold system and to maintain said pressure for a predetermined time interval after the mold system has been filled with molten material.
 28. Dispensing apparatus for high temperature liquids such as molten metal, comprising a non-pressurized reservoir having a discharge port formed in said reservoir formed at the base thereof, a continuous conduit having a choke spool therein and capable of transmitting said liquid substantially in but one direction, a mold system, means for applying suction to the discharge port of said reservoir through said conduit for drawing said liquid from said reservoir to an intermediate receptacle, and means for applying gaseous pressure to said receptacle to drive the liquid therein to said mold system, said conduit substantially opposing the return flow of an excessive amount of said liquid to said reservoir.
 29. Dispensing apparatus for high temperature liquids in accordance with claim 28 including a weir at the base of the reservoir for preventing the flow of such liquid from said reservoir when the level of such liquid in said reservoir is below a predetermined level.
 30. Dispensing apparatus for high temperature liquids according to claim 28 including a mechanical element movable into said reservoir for substantially closing the discharge port thereof when positive pressure is applied to drive the liquid into said mold system.
 31. Dispensing apparatus for high temperature liquids according to claim 28 including also a weir positioned at the discharge port of said reservoir for barring the flow of liquid through the discharge port thereof when the level of the liquid is below the crown of said weir, and a mechanical element to block the flow of liquid through the discharge port when pressure is applied to the mold system.
 32. Dispensing apparatus for liquids according to claim 28 including heating means for supplying heat to the liquid leaving the discharge port of the reservoir to prevent the liquid from solidifying when traveling to the mold system.
 33. A casting system comprising a mold system, a molten metal source, a receptacle fluidically coupled continuously between said mold system and said source and including means for drawing into said receptacle molten metal from said source by suction, means for supplying pressurized gas for feeding molten metal from said receptacle to said mold system, and choke spool means interposed between said receptacle and said source to permit the unidirectional and substantially free flow of molten metal from said source to said receptacle and to substantially obstruct the return flow of liquid from said receptacle to said source, said latter means including an aperture of predetermined cross-sectional shape and dimensions through which the molten metal flows rapidly.
 34. A casting system according to claim 33 in which heat is continuously supplied electrically to said aperture to prevent the molten metal flowing therethrough from solidifying during the time that it remains within said aperture.
 35. A casting system comprising a non-pressurized reservoir containing casting material, a charging tower, a pouring tower, a mold system, substantially airtight couplings fluidically interconnecting said reservoir, said towers and said mold system, means for applying suction to both towers To draw casting material from said reservoir into both towers, means for applying pressure to the charging tower to deliver casting material through the pouring tower to the mold system under continuous pressure supplied to the mold system so as to diminish the presence of voids in the casting material therein.
 36. A casting system according to claim 35 in which the couplings include means to freely transmit casting material from the reservoir to the towers but substantially prevent the excessive flow of casting material in the reverse direction.
 37. A casting system according to claim 35, including means for maintaining the casting material discharged from the reservoir in a continuously fluidic state on its way to the mold system. 